In this lesson, students will learn about biological magnification and how it affects the food web. Students will perform an activity to show how small amounts of pollutants become more concentrated as they move up each trophic level. This lesson relates to previous lessons on food webs, trophic levels, and human impacts on ecosystems.
Objectives
Students will be able to…
Define biological magnification
Explain how the biological magnification of pollution affects the food web
Identify which organism in the food web will be most affected by biological magnification
Preparation notes
Create beakers ahead of time
Do not put them on display until the students are seated
Permission to go outside or use the gym
Let students know that horseplay will not be tolerated
Assign roles and handout worksheets before going outside to begin activity
I will fill 4 beakers with “water samples” and when students are seated, I will place them on the desk at the front of the room. One will be tap water, one will be “aquarium water” (also tap water with maybe some small floating debris), one will be water with algae in it, and the last will be a disgusting looking brown water that looks like sewage. This water will actually be made from iced tea, flat soda, and some unrecognizable solid fragments (crushed raisins, pieces of banana, chocolate syrup, etc). I will make it look as gross as possible.
I will tell the students that these are 4 local water samples. (I will not let them get close enough to them to smell them. They must look from their seats.)
Which one of these do you think is the most polluted?
Which one(s) would you like to drink if you had to?
I will hold up each beaker and poll the students as to which one they would drink. Next I will ask the students which one they would like to see me drink. They will of course choose the disgusting looking one. I will take a big swig of the “sewage water.” After I let them in on the secret of the “sewage water”, I will ask:
What was the point to this demonstration?
If you can’t tell if something is polluted, do you think animals can?
What do you think happens when animals ingest pollutants that humans have released into the ecosystem?
Today we are going to explore how pollutants are passed through the food web and how that affects an ecosystem.
Activity
Read worksheet out loud with students. Discuss the players in this food chain. Review with students that zooplankton are microscopic animals that have structures that allow them to capture food (phytoplankton (producers) or other zooplankton and bacteria); thus, zooplankton represent primary consumers in this food chain. Fish represent secondary consumers, and Eagles (or fisherman) represent tertiary consumers.
Pasta should have already been distributed in a large open space (indoor or outdoor).
Give students their roles: 2-3 Eagles (or fisherman to reinforce human impact), 18-20 zooplankton, 6-8 fish (numbers may change depending on class size but the ratio is what is important). Have each set of people easily identifiable with bandannas, signs with pictures around neck, etc.
Distribute a small paper bag to each student representing a zooplankton - the bag is to represent the gut of each animal.
Give the following instructions: The zooplankton will be the first to look for food. The fish, bird(s) (or fisherman) should wait during this time. At a given signal, the zooplankton enter the area and collect as much food (pasta) as they can, placing the food into their bags. At the end of a short time period (30 sec – 1 min) depending on the size of the area, direct zooplankton to stop searching for food.
Next, allow the fish to search for food (zooplankton) for approximately 15-30 seconds or longer depending on the size of the area. Zooplankton can continue to eat until caught. Birds (or fishers) should still wait off to the side. Each fish should have time to catch one or more zooplankton. Any zooplankton tagged or caught by a fish must give his/her bag to the fish and then proceed to the sidelines.
Next, allow the birds (or fishers) to catch the fish. The same rules are followed. Any fish still alive may hunt for zooplankton. If an eagle catches a fish, the fish must give his/her bag(s) to the eagle/fisher and then proceed to the sidelines. At the end of the time period, return back to the classroom.
Ask any participants holding bags to count the total # of colored pasta pieces they ingested. For each animal represented in the food chain, record the number of colored pasta pieces ingested on an overhead or dry erase board so everyone can see the results.
Next, inform students that the colored pasta pieces represent PCBs. Any surviving animal that has colored pasta now carries PCBs in their fatty tissue (where PCBs are stored). Notice that the fish should have more PCBs than the zooplankton, and the birds/fishers should have even more.
Students will work on their worksheet to answer questions about the activity and about biological magnification.
Closing
So what happened in this activity?
Who ended up with the most PCBs in their bodies?
Why is this important in terms of biodiversity?
Why is this important to humans?
Please finish up your worksheet and hand it in by the end of class. If you have not handed in your draft of your invasive species wanted poster, please do so now.
Overview
In this lesson, students will learn about biological magnification and how it affects the food web. Students will perform an activity to show how small amounts of pollutants become more concentrated as they move up each trophic level. This lesson relates to previous lessons on food webs, trophic levels, and human impacts on ecosystems.
Objectives
Students will be able to…
Preparation notes
Materials
Instruction
Opening
I will fill 4 beakers with “water samples” and when students are seated, I will place them on the desk at the front of the room. One will be tap water, one will be “aquarium water” (also tap water with maybe some small floating debris), one will be water with algae in it, and the last will be a disgusting looking brown water that looks like sewage. This water will actually be made from iced tea, flat soda, and some unrecognizable solid fragments (crushed raisins, pieces of banana, chocolate syrup, etc). I will make it look as gross as possible.
I will tell the students that these are 4 local water samples. (I will not let them get close enough to them to smell them. They must look from their seats.)
I will hold up each beaker and poll the students as to which one they would drink. Next I will ask the students which one they would like to see me drink. They will of course choose the disgusting looking one. I will take a big swig of the “sewage water.” After I let them in on the secret of the “sewage water”, I will ask:
Today we are going to explore how pollutants are passed through the food web and how that affects an ecosystem.
Activity
Closing
Please finish up your worksheet and hand it in by the end of class. If you have not handed in your draft of your invasive species wanted poster, please do so now.
Assessment
Questions in class and pollution worksheet.
Homework
Finish up any work not completed in class.
References:
http://www.ie.unc.edu/erp/resources/PCB_Biomagnification_Activity_with_signs.pdf
Shields, Martin. 2005. Biology Inquiries: Standards-Based Labs, Assessments, and Discussion Lessons.
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